Hi Doug,
I copied the file to
/home/daq/blast/pro2004/Blast_Params/bgrid2.blast, and checked it in
(version 1.9). Note that cvs_v3/Blast_Params is not used, and also the
'2' in bgrid2.blast, and #2 in the first line refer to the file format,
not version of the map. I also fixed the first line.
I started 'setenv ANALDIR test-2005-10-04; lrn +SQL 12144' from the
blast acct to test the new field.
We can either check the larger map as a new version of bgrid2.blast,
or with a new name like 'bgrid2.large', making it easier to switch back
and forth. Which do you think would be better?
--Chris
Douglas Kenneth Hasell wrote:
>
> Hi,
>
> I have put a file "bgrid3.blast" into the Blast_Params sub-
> directory of the blast account. I have not done anything else and hope
> someone who knows what they are doing can take the appropriate action.
>
> This file has the same ranges (ie size) as the previous grid files
> so no changes are needed to the code other than whatever is necessary
> to have the field calculating code point at this file rather than
> bgrid2.blast.
>
> The new file "bgrid3.blast" is based on the field mapping data from
> Abby Goodhue "TOT.dat". I used her results but edited to remove any
> point which differed by more than 200 G from the Biot-Savard
> calculation (this had the effect of removing about 150 bad points). I
> then fit the mapped data allowing the coils to move and obtained a
> good fit with R = -8.1 mm, Z = 8.09 mm, and some small angle changes.
>
> I then filled the desired grid with the closest mapped result if
> one existed and with the offset coil calculated result if no mapped
> data was close. If the calculated point is greater than 4000 G (which
> can happen close to the coils) I fix its magnitude to 4000 G to reduce
> the non-linearities near the coil. Then, since the mapped values are
> not exactly on the grid points I loop over the grid points and
> determined the field at the grid point by fitting a second order
> polynomial in x, y, and z to the 27 points surrounding the desired grid
> point. I do this so long as at least one point of the 27 was a
> measured value. If all 27 are calculated there is no need to do the fit.
>
> I am now calculating a new grid following the same procedure as
> above but changing the ranges so that the grid extends to the TOF's in
> x, y, and z and also extends back to Z = -1.2 m to include the BAT's
>
> The old range was
>
> -200 <= x <= 200
> -70 <= y <= 70
> -10 <= z <= 290
>
> The new range I am calculating now is:
>
> -250 <= x <= 250, 101 grid steps
> -90 <= y <= 90, 37 grid steps
> -120 <= z <= 380, 101 grid steps
>
> For comparison the y component of the field at
>
> x = 200, y = 0, z = 0 is -454 G
> x = 250, y = 0, z = 0 is -95 G (near face of back angle TOF)
>
> x = 130, y = 0, z = 290 is -269 G
> x = 130, y = 0, z = 380 is 10 G (near face of forward angle TOF)
>
> This new grid will be approximately 2.6 times larger. If anyone
> thinks this too large please let me know.
>
>
>
> Cheers,
>
> Douglas
>
> 26-415 M.I.T.
> Tel: +1 (617) 258-7199
> 77 Massachusetts Avenue Fax: +1 (617)
> 258-5440
> Cambridge, MA 02139, USA E-mail:
> hasell@mit.edu
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